JP6459908B2 - Exhaust purification system and purification control device - Google Patents

Description

  The present disclosure relates to an exhaust purification system and a purification control device that purify nitrogen oxides contained in exhaust gas discharged from an engine.

  Conventionally, for example, Patent Document 1 discloses an exhaust purification device that uses a fuel as a reducing agent and purifies nitrogen oxides contained in exhaust gas with a catalyst. Such catalysts are subject to degradation with continued use. Therefore, the exhaust emission control device of Patent Document 1 determines the progress of deterioration of the entire catalyst by detecting the temperature of the catalyst, and corrects the amount of fuel supplied to the catalyst as a reducing agent.

JP 2001-59413 A

  Now, the inventors have focused on the fact that, in the catalyst that has been used continuously, a portion where deterioration has progressed and a portion where deterioration has little existed. As a result, the inventors have found that the exhaust gas purification apparatus of Patent Document 1 has a problem that the performance degradation of the catalyst accompanying deterioration becomes more remarkable than necessary. Specifically, in the exhaust emission control device of Patent Document 1, the entire catalyst is regarded as one, deterioration is determined, and the supply amount of fuel as a reducing agent is adjusted. For this reason, even if a portion with little deterioration remains in the catalyst, the portion with little deterioration cannot sufficiently exhibit the action of purifying nitrogen oxides in the exhaust gas. As a result, the performance degradation of the catalyst due to deterioration has become remarkable.

  The present disclosure has been made in view of such problems, and an object of the present disclosure is to provide an exhaust purification system and a purification control device capable of suppressing a reduction in catalyst performance due to deterioration.

  In order to achieve the above object, according to a first aspect disclosed, a reducing agent that reduces nitrogen oxides contained in exhaust gas exhausted from an engine (ICE) is reformed with a fuel used in the engine. A fuel reformer (20) generated by the above, a catalyst (31) for purifying nitrogen oxides in exhaust gas using a reducing agent supplied by the fuel reformer, and a flow direction of the exhaust gas A plurality of degradation detectors (44a to 44c) that are arranged in the catalyst and detect physical quantities related to the degradation of the catalyst, and based on the detection values of the plurality of degradation detectors, generate a degradation distribution of the catalyst in the flow direction, A deterioration estimating unit (64) for estimating a portion of the catalyst with less deterioration from the deterioration distribution, and a fuel reforming so as to reach the portion of the catalyst with less deterioration estimated by the deterioration estimating unit in an active state. Fuel Reforming control unit that controls the reforming and (65), is an exhaust gas purification system comprising a.

  In this aspect, the reducing agent that reduces the nitrogen oxides contained in the exhaust gas is generated by reforming the fuel by the fuel reformer. Therefore, it is possible to control the activity level of the reducing agent supplied from the fuel reformer. Further, the deterioration estimation unit generates a catalyst deterioration distribution based on detection values of a plurality of deterioration detection units arranged along the flow direction of the exhaust gas, and estimates a portion of the catalyst with less deterioration. If the fuel reformer is controlled so that the reducing agent in an activated state reaches the portion of the catalyst with less deterioration, the portion of the catalyst with less deterioration will preferentially use the activated reducing agent, and the exhaust gas The effect of purifying nitrogen oxides therein can be sufficiently exerted. As a result, an exhaust purification system that can suppress a decrease in catalyst performance due to deterioration is realized.

  The second aspect disclosed is a fuel reformer that generates a reducing agent that reduces nitrogen oxides contained in exhaust gas discharged from an engine (ICE) by reforming the fuel used in the engine. Purification applied to an exhaust purification system (100) comprising a quality device (20) and a catalyst (31) for purifying nitrogen oxides in exhaust gas using a reducing agent supplied by a fuel reformer An information acquisition unit for acquiring a detection value obtained by detecting a physical quantity related to catalyst deterioration from each of a plurality of deterioration detection units (44a to 44c) arranged in the catalyst along the exhaust gas flow direction. (62) and a degradation estimation unit (64) that generates a degradation distribution of the catalyst in the flow direction based on the detection values of the plurality of degradation detection units, and estimates a portion of the catalyst with less degradation from the degradation distribution; Deterioration estimation And a reforming control unit (65) for controlling reforming of the fuel by the fuel reformer so as to reach the portion with less degradation estimated by the above in a state where the reducing agent is activated. .

  Also according to this aspect, nitrogen oxides can be sufficiently purified by preferentially using a reducing agent in which a portion of the catalyst with little deterioration is activated, and therefore, a reduction in catalyst performance due to deterioration is suppressed.

  Note that the reference numbers in the parentheses merely show an example of a correspondence relationship with a specific configuration in an embodiment described later, and do not limit the scope of the present invention.

1 is an overall view showing an overall configuration of an exhaust purification system according to a first embodiment together with an internal combustion engine. It is a figure which shows the functional block for the post-process constructed | assembled by ECU. It is a figure which shows the specific aspect of the reference temperature distribution of NOx catalyst, and measured temperature distribution. It is a flowchart which shows the detail of a reforming control process. It is a flowchart which shows the detail of execution determination processing of deterioration diagnosis. It is a flowchart which shows the detail of a degradation estimation process. It is a figure which shows the correlation with the temperature and air fuel ratio in a reforming catalyst, and the reforming state of a fuel. It is a flowchart which shows the detail of the reforming control process of 2nd embodiment. It is a figure which shows the specific example of the steady state in which deterioration diagnosis is implemented in 2nd embodiment. It is a figure which compares and shows distribution of the actually generated heat in a NOx catalyst, and the distribution of the estimated generated heat. It is a flowchart which shows the detail of a reforming adjustment process.

  Hereinafter, a plurality of embodiments of the present disclosure will be described based on the drawings. In addition, the overlapping description may be abbreviate | omitted by attaching | subjecting the same code | symbol to the corresponding component in each embodiment. When only a part of the configuration is described in each embodiment, the configuration of the other embodiment described above can be applied to the other part of the configuration. Moreover, not only the combination of the configurations explicitly described in the description of each embodiment, but also the configuration of a plurality of embodiments can be partially combined even if they are not explicitly described, as long as there is no problem in the combination. And the combination where the structure described in several embodiment and the modification is not specified shall also be disclosed by the following description.

(First embodiment)
An exhaust purification system 100 according to the first embodiment shown in FIG. 1 is mounted on a vehicle together with an internal combustion engine ICE and the like. The internal combustion engine ICE is a compression self-ignition diesel engine and is a power source for running the vehicle. The internal combustion engine ICE generates power by burning light oil.

  The internal combustion engine ICE is provided with a supercharger 11, an intercooler 14, and the like. An intake pipe 12 and an exhaust pipe 13 are connected to the supercharger 11. The intake pipe 12 forms an intake passage through which air is circulated to the compressor portion of the supercharger 11. The exhaust pipe 13 forms an exhaust passage through which exhaust gas flows from the turbine section of the supercharger 11 to the exhaust purification system 100.

  In the following description, the upstream side and the downstream side are defined based on the flow directions of air and exhaust gas. That is, the upstream side of the intake pipe 12 indicates the side close to the compressor section, and the downstream side of the exhaust pipe 13 indicates the side close to the turbine section.

  The exhaust purification system 100 is provided in the exhaust system 90 of the internal combustion engine ICE. The exhaust purification system 100 is a post-processing system that purifies substances generated by the combustion of light oil in the internal combustion engine ICE. The exhaust purification system 100 purifies by decomposing nitrogen oxides (NOx) into nitrogen (N2) among substances contained in exhaust gas discharged from the internal combustion engine ICE. The exhaust purification system 100 includes a fuel reformer 20, a NOx purification device 30, a fresh air introduction device 81, and an engine control unit (hereinafter referred to as ECU) 50.

  The fuel reformer 20 is provided in the middle of the exhaust pipe 13. In the exhaust pipe 13, an aftertreatment device such as an oxidation catalyst and a diesel particulate filter is further provided between the supercharger 11 and the fuel reformer 20. The fuel reformer 20 generates reformed fuel by reforming fuel (light oil). The reformed fuel is a reducing agent used for NOx reduction in the NOx purification device 30. The fuel used for generating the reducing agent in the fuel reformer 20 is shared with the fuel used for generating power in the internal combustion engine ICE. The fuel reformer 20 supplies the reducing agent to the NOx purification device 30 through the exhaust passage. The fuel reformer 20 includes a fuel injection valve 21, a housing 24, a temperature riser 22, and a reforming catalyst 23.

  The fuel injection valve 21 is located upstream of the reforming catalyst 23 and is attached to the exhaust pipe 13 or the housing 24. The fuel injection valve 21 is connected to the fuel pump 72. The fuel stored in the fuel tank 71 is supplied to the fuel injection valve 21 by the operation of the fuel pump 72. The fuel injection valve 21 has one or a plurality of injection holes facing the exhaust passage. The fuel injection valve 21 injects fuel from the injection hole by generating an electromagnetic force in the electromagnetic solenoid. The fuel injection valve 21 supplies the fuel atomized by passing through the injection hole to the reforming catalyst 23.

  The housing 24 is formed in a container shape by a thin metal plate. The housing 24 accommodates the temperature increaser 22 and the reforming catalyst 23. The housing 24 is connected to the exhaust pipe 13 and forms a part of the exhaust passage.

  The heater 22 is a heating element that generates heat when energized. The temperature raising device 22 is disposed integrally with the reforming catalyst 23. The amount of heat generated by the temperature raising device 22 is transmitted to the reforming catalyst 23 to raise the temperature of the reforming catalyst 23. The temperature riser 22 indirectly raises the temperature of the fuel injected by the fuel injection valve 21 to make it easy to activate.

  The reforming catalyst 23 is a monolithic catalyst in which, for example, cordierite formed in a honeycomb shape is coated with zeolite or aluminum oxide (Al2O3, hereinafter referred to as alumina). Due to the catalytic action of the reforming catalyst 23, the hydrocarbon that is the main component of the fuel is partially oxidized. As a result, for example, a partial oxide (for example, an aldehyde) oxidized to an aldehyde group (CHO), or carbon monoxide (CO), hydrogen (H2), etc. as a reforming fuel that functions as a reducing agent, fuel reforming Supplied from the device 20.

  The NOx purification device 30 includes a NOx catalyst 31 and a metal housing 35 that houses the NOx catalyst 31. The NOx catalyst 31 purifies NOx in the exhaust gas using the reformed fuel. The NOx catalyst 31 is a monolith catalyst having a carrier 32 and a catalyst metal 33 and formed in a honeycomb shape. The carrier 32 is, for example, alumina. The carrier 32 is a base material that supports the catalyst metal 33. The catalyst metal 33 is, for example, silver (Ag). The catalytic metal 33 is located on the surface of the support 32 and promotes the reduction reaction of NOx.

  As the support 32, in addition to the above-described alumina, one or more of zeolite, silica, titania, ceria, and zirconia can be used. In addition to the above-mentioned silver, copper (Cu), platinum (Pt), palladium (Pd), nickel (Ni), iridium (Ir), radium (Rh) or the like can be used as the catalyst metal 33. is there. Further, cobalt (Co), osmium (Os), ruthenium (Ru), iron (Fe), rhenium (Re), technetium (Tc), manganese (Mn), titanium (Ti), etc. are used as the catalyst metal 33. Also good. In addition, the above metal may be supported on the support 32 in an oxide state. Further, a plurality of types of the above metals may be supported on the carrier 32 as a single substance or as an oxide.

  The NOx catalyst 31 adsorbs NOx in the exhaust gas flowing into the NOx purification device 30 when the catalyst temperature is low (less than about 200 ° C.). On the other hand, when the catalyst temperature becomes high (about 200 ° C. or higher), the NOx catalyst 31 desorbs the adsorbed NOx. The desorbed NOx reacts with the reformed fuel supplied from the fuel reformer 20 by the catalytic action of the NOx catalyst 31. As the reformed fuel functions as a reducing agent, NOx is reduced to nitrogen. Although the exhaust gas contains oxygen (O2) in addition to NOx, the reformed fuel selectively reacts with NOx even in the presence of oxygen.

  The fresh air introduction device 81 includes a fresh air introduction pipe 82, an introduction control valve 83, and the like. The fresh air introduction pipe 82 is formed of a reinforced rubber hose material, a curved metal tubular member, or the like. One end of the fresh air introduction pipe 82 is connected to a portion located on the downstream side of the intercooler 14 in the intake system. The other end of the fresh air introduction pipe 82 is connected to a portion of the exhaust pipe 13 that is located upstream of the reforming catalyst 23. The fresh air introduction pipe 82 forms an introduction passage through which the air that has passed through the intercooler 14 is introduced into the fuel reformer 20.

  The introduction control valve 83 is provided in the middle of the fresh air introduction pipe 82. The introduction control valve 83 switches the introduction passage between a communication state and a cutoff state. The introduction control valve 83 is configured by combining an electromagnetic valve whose opening and closing is controlled by the ECU 50 and a check valve that prevents backflow of air and exhaust gas from the exhaust passage to the intake passage.

  The ECU 50 is a control device that integrally performs control related to the internal combustion engine ICE. The ECU 50 is mainly configured by a microcomputer having a processor 51, a RAM 52, a storage medium 53, and an input / output interface 54 for measurement signals and control signals. The ECU 50 is connected to a plurality of in-vehicle sensors 40. The in-vehicle sensor 40 includes a sensor that detects driver operation information input to an accelerator pedal, a steering, and the like, and a sensor that detects operation information related to the internal combustion engine ICE such as a rotation speed and an intake air temperature.

  In addition, the ECU 50 is connected with a fuel injection valve 21, a temperature riser 22, a fuel pump 72, and an introduction control valve 83 as a configuration related to post-processing. Further, an exhaust gas sensor 41, an inlet temperature sensor 43, a plurality (three) of catalyst temperature sensors 44a to 44c, a reducing agent sensor 45, an outside air temperature sensor 47, an air flow meter 49, and the like are connected to the ECU 50.

  The exhaust gas sensor 41 is configured by combining an O2 sensor that outputs a signal corresponding to the oxygen concentration in the exhaust gas and a NOx sensor that outputs a measurement signal corresponding to the NOx concentration in the exhaust gas. The exhaust gas sensor 41 is arranged on the upstream side of the reforming catalyst 23 and detects the oxygen concentration and NOx concentration of the exhaust gas flowing into the reforming catalyst 23.

  The inlet temperature sensor 43 and the catalyst temperature sensors 44a to 44c are thermocouples or thermistors. The inlet temperature sensor 43 is disposed upstream of the NOx catalyst 31 and outputs a measurement signal corresponding to the temperature of the exhaust gas flowing into the NOx catalyst 31. Each catalyst temperature sensor 44 a to 44 c is attached to the housing 35. A plurality of catalyst temperature sensors 44a to 44c are arranged on the NOx catalyst 31 while being spaced apart from each other along the flow direction of the exhaust gas. Each of the catalyst temperature sensors 44a to 44c detects the temperatures of a plurality of locations of the NOx catalyst 31 as one of physical quantities related to catalyst deterioration, and outputs a measurement signal corresponding to the catalyst temperature.

  The reducing agent sensor 45 is attached to a section of the exhaust pipe 13 between the fuel reformer 20 and the NOx purification device 30. The reducing agent sensor 45 is located between the reforming catalyst 23 and the fuel injection valve 21 and detects the state of the reducing agent supplied from the reforming catalyst 23. For example, the reducing agent sensor 45 determines the type of hydrocarbon that has passed through the reforming catalyst 23 and outputs a measurement signal corresponding to the determination result.

  The outside air temperature sensor 47 outputs a measurement signal corresponding to the temperature outside the vehicle. The air flow meter 49 is provided in the intake pipe 12. The air flow meter 49 is a sensor having a platinum hot wire or the like, and outputs a measurement signal corresponding to the flow velocity of the air flowing through the intake passage. Based on the measurement signal of the air flow meter 49, the flow rate of the intake air supplied to the internal combustion engine ICE is acquired by the ECU 50.

  The ECU 50 constructs the information acquisition unit 62, the steady state determination unit 63, the deterioration estimation unit 64, and the reduction control unit 65 shown in FIG. 2 as functional blocks related to the post-processing of NOx by executing the exhaust gas purification processing program by the processor 51. To do. Hereinafter, details of each functional block constructed in the ECU 50 will be described with reference to FIGS. 2 and 1.

  For example, as information related to post-processing, the information acquisition unit 62 detects a temperature at each location of the NOx catalyst 31 as a physical quantity related to deterioration of the NOx catalyst 31 from each of the catalyst temperature sensors 44a to 44c. To get. In addition, the information acquisition unit 62 acquires NOx and oxygen concentration contained in the exhaust gas based on the measurement signal of the exhaust gas sensor 41. Further, the information acquisition unit 62 acquires the temperature of the exhaust gas flowing into the NOx purification device 30 based on the measurement signal of the inlet temperature sensor 43. Further, the information acquisition unit 62 acquires the type and supply amount of reformed hydrocarbons supplied to the NOx catalyst 31 based on the measurement signal of the reducing agent sensor 45.

  The information acquisition unit 62 acquires operation information indicating the operation state of the internal combustion engine ICE in time series. The information acquisition unit 62 can detect an abnormal state of the internal combustion engine ICE based on the acquired operation information. The operation information includes a fuel injection amount injected into the combustion chamber in the internal combustion engine ICE, a gas flow rate of the exhaust gas, and the like. The gas flow rate is calculated by the information acquisition unit 62 using the intake air flow rate detected by the air flow meter 49, the intake air temperature acquired from the in-vehicle sensor 40, the exhaust gas temperature detected by the inlet temperature sensor 43, and the like. The The gas flow rate may be directly detected by a flow sensor provided in the exhaust pipe 13.

  The steady state determination unit 63 determines whether or not the internal combustion engine ICE is in a steady state based on the transition of the operation information acquired by the information acquisition unit 62. Specifically, the steady state determination unit 63 determines that the steady state is satisfied when fluctuations in the flow rate of intake air or the flow rate of exhaust gas, the fuel injection amount, and the like are within a predetermined range due to idling or constant speed running. It is determined that

  The deterioration estimation unit 64 uses a temperature of each part of the NOx catalyst 31 to perform a deterioration estimation process (see FIG. 6), which will be described later. Estimate the few parts. The deterioration estimation unit 64 uses the exhaust gas temperature that is the detection value of the inlet temperature sensor 43 and the catalyst temperatures T01 to T03 that are the detection values of the catalyst temperature sensors 44a to 44c, and the NOx catalyst 31 along the flow direction. Get the temperature distribution of. In the vicinity of the deteriorated portion of the NOx catalyst 31, the reaction of the reducing agent hardly occurs. Therefore, the actually measured temperature distribution can be regarded as a deterioration distribution indicating the degree of deterioration of each part of the NOx catalyst 31. When the upstream side (hereinafter referred to as the front side) of the NOx catalyst 31 in the flow direction is deteriorated, the temperature distribution has a shape in which the peak position is shifted backward (see the long broken line in FIG. 3). Moreover, when the downstream part (henceforth, back) of the flow direction of NOx catalyst 31 has deteriorated, temperature distribution becomes a shape which the back part fell (refer the short broken line of FIG. 3).

  The deterioration estimation unit 64 determines the degree of deterioration of each part of the NOx catalyst 31 by comparing the acquired temperature distribution with a reference temperature distribution (see the solid line in FIG. 3). The reference temperature distribution is acquired by correcting standard data created in advance using the exhaust gas temperature actually measured by the inlet temperature sensor 43. Therefore, the reference temperature distribution value T00B at the position of the inlet temperature sensor 43 is substantially the same as the temperature T00 actually measured by the inlet temperature sensor 43. Further, the standard data of the reference temperature distribution is the catalyst temperature assumed to be shown in the NOx catalyst 31 before deterioration when the internal combustion engine ICE is operated by injection of a predetermined fuel amount under predetermined operating conditions. Distribution. The standard data is stored in the storage medium 53 in the form of map data or mathematical expressions.

  Here, when it is assumed that the entire NOx catalyst 31 is not deteriorated, the reducing agent causes many reduction reactions in the front portion of the NOx catalyst 31. And it is estimated that the consumption of a reducing agent decreases gradually as it goes to the rear part of the NOx catalyst 31. On the other hand, in the NOx catalyst 31 in which the front portion has deteriorated, the reducing agent that undergoes a reduction reaction in the front portion is reduced as compared with the NOx catalyst 31 in which the whole is undegraded. Therefore, the amount of the reducing agent that reaches the intermediate portion of the NOx catalyst 31 increases, and the catalyst temperature rises downstream of the intermediate portion. The deterioration estimation unit 64 can correct the shift of the peak position in the reference temperature distribution to the downstream side in order to reflect the change in the amount of the reducing agent that reaches the upstream side and the change in the exhaust gas temperature. (See the two-dot chain line in FIG. 3).

More specifically, the storage medium 53 stores the following formulas 1 and 2 for calculating the catalyst temperature T_cat at each location of the NOx catalyst 31.
(Equation 1) T_cat = T_in−T_loss + T_rea
(Equation 2) T_rea = Q_in × η
Here, T_in in Equation 1 above indicates the temperature of the inflowing exhaust gas, T_loss indicates a temperature decrease caused by heat dissipation, and T_rea indicates a temperature increase associated with the reduction reaction of the reducing agent. T_loss is corrected using, for example, the outside air temperature measured by the outside air temperature sensor 47, the traveling speed measured by the in-vehicle sensor 40, and the like. Q_in indicates the inflow amount of the reducing agent that reaches each place, and η indicates the reaction rate of the reducing agent. The reaction rate η is uniquely set from the temperature of each part of the catalyst by a preset function map.

  According to the above formulas 1 and 2, when the front portion of the NOx catalyst 31 deteriorates, the exhaust gas temperature (T_in) flowing into the intermediate portion decreases. Therefore, since the amount of heat lost due to heat radiation is reduced, the temperature drop value (T_loss) is also reduced. On the other hand, the value (T_rea) of the temperature rise accompanying the reduction reaction increases due to the increase in the inflow amount (Q_in) of the reducing agent that reaches the intermediate portion. As a result, the deterioration estimation unit 64 generates a reference temperature distribution in which the temperature peak position is slid downstream as described above (see the two-dot chain line in FIG. 3).

  The reduction control unit 65 controls fuel reforming by the fuel reforming apparatus 20 based on a plurality of reforming control maps created in advance. The plurality of reforming control maps are stored in the storage medium 53. The reforming control map defines the control amounts of the temperature raising device 22, the fuel injection valve 21, the fuel pump 72, and the introduction control valve 83 with respect to the catalyst temperature. The reduction control unit 65 can supply the reducing agent to the NOx catalyst 31 in a reformed state optimal for NOx purification by controlling each component corresponding to the current catalyst temperature based on the reforming control map. . When the NOx catalyst 31 is substantially non-deteriorated, the catalyst temperature used for referring to the reforming control map may be, for example, a detection value of the intermediate catalyst temperature sensor 44b, or each of the catalyst temperature sensors 44a to 44c. May be the average of the detected values.

  The reduction control unit 65 can correct the reforming state of the fuel by the fuel reformer 20 in accordance with the deterioration of the NOx catalyst 31 by performing a reforming control process (see FIG. 4) described later. Therefore, the reduction control unit 65 acquires an estimation result obtained by estimating the deterioration degree of the NOx catalyst 31 from the deterioration estimation unit 64. Based on the estimation result of the deterioration estimation unit 64, the reduction control unit 65 reforms the fuel by the fuel reformer 20 so that the portion of the NOx catalyst 31 that has little deterioration reaches the reduced agent in an activated state. Control.

  Specifically, the reduction control unit 65 controls the activity of the reducing agent supplied from the fuel reforming device 20 to be lower as the portion of the NOx catalyst 31 that has progressed deteriorates downstream in the flow direction. To do. According to the above, the position where the active state suitable for the reduction of NOx is shifted to the downstream side of the NOx catalyst 31 along the flow direction. As a result, the reduction reaction of NOx occurs actively in the middle to the rear part of the NOx catalyst 31 with little deterioration.

  For example, when an abnormal temperature rise occurs in the rear portion of the NOx catalyst 31 and the rear portion deteriorates, the reduction control unit 65 increases the activity of the reducing agent supplied from the fuel reformer 20. Control. According to the above, the position where the active state suitable for NOx reduction is maintained on the upstream side of the NOx catalyst 31. As a result, the reduction reaction of NOx occurs actively in the middle portion from the front of the NOx catalyst 31 with little deterioration.

  Next, the processes performed by the deterioration estimation unit 64 and the reduction control unit 65 described so far are organized and described based on the flowcharts of FIGS. 4 to 6 with reference to FIGS. First, the details of the reforming control process will be described based on the flowchart of FIG. The reforming control process is performed at a timing when deterioration diagnosis is required, such as when a certain period has elapsed since the previous deterioration diagnosis, or when an abnormal state of the internal combustion engine ICE is detected by the information acquisition unit 62. 65 starts.

  Here, the abnormal state of the internal combustion engine ICE is a state in which instantaneous catalyst deterioration is feared, such as an abnormal temperature rise of the NOx catalyst 31 and an excessive decrease in the oxygen concentration in the exhaust passage. When such an abnormal state occurs, the reforming control process is started in order to confirm whether or not the function of the NOx catalyst 31 is lost.

  In S101, deterioration diagnosis execution determination processing (see FIG. 5) is performed to determine whether or not deterioration diagnosis is possible. If it is determined in S101 that the diagnosis start condition is not satisfied, the reforming control process is terminated. On the other hand, when it is determined in S101 that the diagnosis start condition is satisfied, the process proceeds to S102. In S102, in order to diagnose the degree of deterioration of the NOx catalyst 31, a predetermined amount of fuel is injected in a preset pattern, and the process proceeds to S103. The reducing agent for diagnosis is supplied to the NOx catalyst 31 through S102. The diagnostic fuel injection pattern implemented in S102 is a fuel injection pattern that is substantially the same as or correlated with the fuel injection pattern used when generating standard data of the reference temperature distribution.

  In S103, it is determined whether or not a predetermined time has elapsed since the supply of the reducing agent was started in S102. The specified time in S103 is a time for waiting for stabilization of the reduction reaction in the NOx purification device 30, and is set to, for example, several tens of seconds to about 1 minute. If it is determined in S103 that the specified time has elapsed and the reduction reaction by the reducing agent for diagnosis is estimated to be stable, the process proceeds to S104.

  In S104, the deterioration estimation unit 64 performs the deterioration distribution estimation process (see FIG. 6), and the process proceeds to S105. In S105, based on the degradation distribution estimation process in S104, the presence or absence of a catalyst portion whose degradation is estimated is determined. If it is determined in S105 that the NOx catalyst 31 does not have a portion where deterioration is estimated, the reforming control process is terminated. On the other hand, if it is determined in S105 that the deteriorated portion is in the NOx catalyst 31, the process proceeds to S106.

  In S106, the part where deterioration is estimated is determined. If it is determined in S106 that the rear portion of the NOx catalyst 31 has deteriorated (see the short broken line in FIG. 3), the process proceeds to S107. In this case, in order to make the front portion of the NOx catalyst 31 estimated to be non-degraded or slightly degraded actively function, control for optimizing the reducing agent species after reforming is started. Therefore, in S107, the catalyst temperature used when referring to the reforming control map is set using the detected values of the catalyst temperature sensors 44a and 44b arranged in front and in the middle of the NOx catalyst 31, and the process proceeds to S108. The catalyst temperature may be a value obtained by averaging the detected values of the catalyst temperature sensors 44a and 44b, or may be a value obtained by weighting the detected values according to the forward and intermediate degree of deterioration.

  In S108, a correction amount of control for the fuel reformer 20 or the like so that the reducing agent is easily supplied from the fuel reformer 20 in a state of being reformed into a hydrocarbon (for example, aldehyde or the like) that has been made highly active in advance. Is set, and the reforming control process ends. The setting of the correction amount in S108 is realized by changing the reforming control map to be referred to, for example.

  In S108, control is performed to raise (increase) the temperature of the heater 22 in accordance with the nature of the fuel (see FIG. 7) that is likely to be reformed to a higher activity as the temperature increases. In addition, in S108, the amount of fuel injected from the fuel injection valve 21 per unit time is adjusted to be small in accordance with the nature of the fuel (see FIG. 7) that is more easily reformed as the air-fuel ratio becomes leaner. To do. Specifically, the injection amount per shot is reduced by reducing the injection pressure of the fuel injection valve 21 by controlling the fuel pump 72 and shortening the valve opening time of the injection. In addition, the fuel supply amount is secured by controlling the injection frequency to be high. Further, in S108, the air-fuel ratio in the vicinity of the reforming catalyst 23 is adjusted to the lean side by increasing the amount of fresh air introduced by controlling the introduction control valve 83.

  On the other hand, when it determines with the front part of the NOx catalyst 31 having deteriorated in S106 (refer the long broken line of FIG. 3), it progresses to S109. In this case, in order to make the rear part of the NOx catalyst 31 estimated to be non-degraded or slightly degraded actively function, control for optimizing the reducing agent species after reforming is started. Therefore, in S109, the catalyst temperature used when referring to the reforming control map is set using the detected values of the catalyst temperature sensors 44b and 44c arranged in the middle and rear of the NOx catalyst 31, and the process proceeds to S110. The catalyst temperature may be a value obtained by averaging the detected values of the catalyst temperature sensors 44b and 44c, or may be a value obtained by weighting the detected values according to the intermediate and rear deterioration levels.

  In S110, a correction amount of control for the fuel reformer 20 or the like is set so that the fuel is supplied from the fuel reformer 20 with low activity, and the reforming control process is terminated. The setting of the correction amount in S110 is realized by, for example, changing the reforming control map to be referred to, as in S108.

  In S110, correction opposite to that in S108 is performed. That is, in S110, the temperature of the heater 22 is controlled to be lowered (suppressed) to suppress the temperature rise of the fuel. Further, in S110, the amount of fuel injected per unit time is adjusted to be large. Specifically, the injection amount per shot is increased by increasing the injection pressure of the fuel injection valve 21 by controlling the fuel pump 72 and extending the opening time of the injection. In addition, the injection frequency is adjusted low to prevent excessive fuel supply. Further, the amount of fresh air introduced is reduced by controlling the introduction control valve 83, and the air-fuel ratio in the vicinity of the reforming catalyst 23 is adjusted to the rich side.

  In S108 and S110 described above, the reformed state of the target reformed fuel is set. The reduction control unit 65 controls the heater 22, the fuel injection valve 21, and the like so that the state of the reducing agent acquired as the detection result of the reducing agent sensor 45 approaches the reformed state set as a target. Feedback control is performed based on the detected value of 45. As a result of such control, when the detection value of the reducing agent sensor 45 does not asymptotically reach the target reforming state, the reduction control unit 65 diagnoses that the reforming catalyst 23 has deteriorated or malfunctioned.

  Next, details of the execution determination process for deterioration diagnosis performed in S101 of the reforming control process will be described based on the flowchart of FIG.

  In S121, it is determined whether or not the warm-up operation of the internal combustion engine ICE has ended. If it is determined in S121 that the warm-up operation is being performed, the execution determination process and the reforming control process are terminated. On the other hand, if it is determined in S121 that the warm-up operation of the internal combustion engine ICE has ended, the process proceeds to S122.

  In S122, the steady state determination unit 63 determines whether or not the internal combustion engine ICE is in a predetermined operation state, that is, in a steady state. In order to realize highly accurate deterioration estimation, it is desirable to perform diagnosis in a state where the fluctuation of the driving state is small. In S122, when it is determined that the fluctuations are large and the internal combustion engine ICE is not in a steady state (unsteady state) based on changes in the gas flow rate of the exhaust gas, the fuel consumption, etc., the execution determination process and the reforming control are performed. End the process. On the other hand, when it is determined in S122 that the internal combustion engine ICE is in a steady state, the execution determination process is terminated, and the process proceeds to S102 of the reforming control process.

  Next, details of the degradation estimation process performed by the degradation estimation unit 64 based on S104 of the reforming control process will be described based on the flowchart of FIG.

  In S141, detection values are acquired from the inlet temperature sensor 43 and the catalyst temperature sensors 44a to 44c. Then, based on the acquired detection values of the temperature sensors 43, 44a to 44c, a temperature distribution of the NOx catalyst 31 along the flow direction (see the broken lines in FIG. 3) is created, and the process proceeds to S142. In S142, a reference temperature distribution is calculated based on the exhaust gas temperature acquired in S141 (see the solid line in FIG. 3). Then, the catalyst temperatures T01 to T03 at each position in the actually measured distribution created in S141 are individually compared with the temperatures T01B to T03B on the calculated reference temperature distribution, and the process proceeds to S143.

  In S142 described above, the comparison between the actually measured catalyst temperatures T01 to T03 and the calculated reference temperatures T01B to T03B is sequentially performed from the upstream side. That is, in the first S142, the catalyst temperature T01 is compared with the reference temperature T01B for the measurement position of the catalyst temperature sensor 44a arranged on the most upstream side. In the second S142, the catalyst temperature T02 and the reference temperature T02B are compared with respect to the measurement position of the catalyst temperature sensor 44b disposed in the middle. In the third S142, the catalyst temperature T03 is compared with the reference temperature T03B for the measurement position of the catalyst temperature sensor 44c arranged on the most downstream side.

  In S143, based on the comparison result in S142, the deterioration of the catalyst portion that has been subjected to the temperature comparison is determined from the temperature difference between the catalyst temperature and the reference temperature. If the measured catalyst temperatures T01 to T03 are approximately the same as the reference temperatures T00B to T03B in S143, it is determined that the catalyst portion subjected to the temperature comparison is non-degraded or slightly degraded, and the process proceeds to S145. . On the other hand, if the measured catalyst temperatures T01 to T03 are lower than the respective reference temperatures T00B to T03B as a result of the temperature comparison in S143, it is determined that the catalyst portion subjected to the temperature comparison has deteriorated, and the process proceeds to S144. .

  In S144, based on the determination that the front of the NOx catalyst 31 is deteriorated, the reference temperature distribution is corrected assuming that the reducing agent that reacts in the middle or rear of the NOx catalyst 31 has increased (two points in FIG. 3). Step S145).

  In S145, it is determined whether or not the comparison between the measured catalyst temperature and the reference temperature has been completed for all measurement positions where the catalyst temperature sensors 44a to 44c are arranged. If it is determined in S145 that there is a measurement position that has not been compared, the process returns to S142, and the most upstream catalyst temperature among the remaining measurement positions is compared with the reference temperature. If the temperature comparison of all measurement positions is completed by repeating S142 to S144, the deterioration estimation process is terminated, and the process proceeds to S105.

  In the first embodiment described so far, the reducing agent is generated by reforming the fuel by the fuel reformer 20. Therefore, it is possible to control the activity level of the reducing agent supplied from the fuel reformer 20. Moreover, the deterioration estimation part 64 can produce | generate the temperature distribution of the NOx catalyst 31, and can estimate the catalyst part with little deterioration from the produced | generated temperature distribution. If the fuel reforming apparatus 20 is controlled so that the reducing agent in an activated state reaches the catalyst portion with less deterioration, the catalyst portion with less deterioration uses the activated reducing agent preferentially in the exhaust gas. The effect of purifying NOx can be sufficiently exerted. As a result, the exhaust purification system 100 that can suppress the performance degradation of the NOx catalyst 31 due to deterioration is realized.

  In addition, the deterioration of the NOx catalyst 31 usually expands from the upstream side to the downstream side along the flow direction. Further, the reformed fuel is gradually activated in the exhaust gas in the process of flowing from the fuel reformer 20 to the NOx catalyst 31. Therefore, as in the first embodiment, if adjustment is made to reduce the activity of the reformed fuel supplied from the fuel reformer 20 with the expansion of the deterioration range of the NOx catalyst 31, the reformed fuel as the reducing agent is reduced. When the catalyst portion that has not deteriorated is reached, an active state suitable for the activity of NOx can be obtained. Therefore, the catalyst portion with less deterioration can reliably exhibit the action of purifying NOx in the exhaust gas.

  In the first embodiment, the amount of fuel injected from the fuel injection valve 21 per unit time is increased in order to make the reformed fuel less active. Furthermore, in 1st embodiment, in order to make reformed fuel low activity, the temperature of the temperature rising device 22 is restrained low. According to these controls, the reformed fuel is delayed in activation in the exhaust gas, and can reach an active state suitable for NOx reduction when it reaches a non-degraded portion. Therefore, the portion of the catalyst that is less deteriorated can purify NOx in the exhaust gas by using a reducing agent that is in an active state suitable for the reduction reaction.

  In addition, in the first embodiment, the temperature distribution by each of the catalyst temperature sensors 44a to 44c is used as a deterioration distribution indicating the degree of progress of deterioration. In the vicinity of the portion of the NOx catalyst 31 where the deterioration has progressed, the reduction reaction is less likely to occur, so the catalyst temperature has a lower value than the state before the deterioration. Therefore, by detecting the temperature at a plurality of locations of the NOx catalyst 31 and comparing it with a reference temperature distribution based on the current exhaust gas temperature or the like, the portion of the NOx catalyst 31 in which deterioration has progressed can be easily and reliably performed. It becomes possible to estimate.

  In the first embodiment, supply of a reducing agent for diagnosis is started when a preset diagnosis start condition is satisfied. With such a configuration, the deterioration estimating unit 64 can estimate the degree of deterioration of the NOx catalyst 31 under conditions where the operating state of the internal combustion engine ICE is stable. As a result, the reducing agent whose reforming state is optimally adjusted in accordance with the current deterioration state of the NOx catalyst 31 reaches the NOx catalyst 31.

  Furthermore, the reduction control unit 65 of the first embodiment determines the type of hydrocarbon from the detection value of the reducing agent sensor 45, and creates a target reforming state by performing feedback control. Therefore, the reduction control unit 65 can accurately control the degree of activity of the reformed fuel released from the fuel reformer 20. According to the above, the reducing agent in a state suitable for the reduction of NOx reliably reaches the portion of the NOx catalyst 31 that is less deteriorated. Further, the deterioration diagnosis of the reforming catalyst 23 can be performed based on the detection value of the reducing agent sensor 45.

  In the first embodiment, the fresh air introduction device 81 can introduce air into the fuel reformer 20. With such a configuration, the adjustment range of the air-fuel ratio and the temperature of the exhaust gas flowing into the fuel reformer 20 is expanded. As a result, the reduction control unit 65 can control the degree of activity of the reformed fuel released from the fuel reformer 20 more freely.

  Furthermore, in the first embodiment, the introduction of air into the fuel reformer 20 is realized by the fresh air introduction pipe 82 branched from the downstream pipe of the intercooler 14. With such a configuration, it is possible to introduce air into the high-pressure intake passage without adding a configuration for pumping air such as a pump.

  In the first embodiment, the internal combustion engine ICE corresponds to an “engine”, the fuel reformer 20 corresponds to a “fuel reformer”, the fuel injection valve 21 corresponds to a “fuel injector”, and The warmer 22 corresponds to a “heating part”, and the NOx catalyst 31 corresponds to a “catalyst”. The reducing agent sensor 45 corresponds to a “reducing agent detection unit”, the ECU 50 corresponds to a “purification control device”, the reduction control unit 65 corresponds to a “reformation control unit”, and the fresh air introduction device 81 corresponds to “ Corresponds to the “new air introduction part”.

(Second embodiment)
The second embodiment shown in FIGS. 8 to 11 is a modification of the first embodiment. In the reforming control process according to the second embodiment, the degree of deterioration of the NOx catalyst 31 is estimated during the period in which the internal combustion engine ICE is operating in a steady state. The details of the reforming control process of the second embodiment will be described below with reference to FIGS. 1 and 2 based on the flowchart of FIG. Similar to the first embodiment, this reforming control process is started by the reduction control unit 65 when a certain period has elapsed since the last deterioration diagnosis or when an abnormal state of the internal combustion engine ICE is detected. The

  In S201, it is determined whether or not the deterioration diagnosis can be started based on the operation fluctuation of the internal combustion engine ICE. Specifically, in S201, as the operation information indicating the operation variation of the internal combustion engine ICE, the gas flow rate of the exhaust gas, the fuel injection amount, and the like are continuously monitored by the steady state determination unit 63 for a predetermined monitoring time. Then, it is determined whether or not fluctuations such as the gas flow rate and the fuel injection amount are within a predetermined fluctuation range set as a threshold value for a predetermined period (see the dot area in FIG. 9). As a result, it is determined that the deterioration diagnosis can be started when the fluctuations in the gas flow rate and the fuel injection amount continue within the respective threshold values over a certain period, and the process proceeds to S202. On the other hand, when it is determined that the fluctuations in the gas flow rate and the fuel injection amount are so severe that the deterioration diagnosis cannot be started, the reforming control process is terminated.

  In S202, the temperature distribution along the flow direction of the NOx catalyst 31 using detected values detected from the inlet temperature sensor 43 and the catalyst temperature sensors 44a to 44c at the end of the period in which the internal combustion engine ICE has maintained a steady state. And proceeds to S203. Also in the second embodiment, the temperature distribution based on the detection values of the temperature sensors 43, 44a to 44c can be regarded as the deterioration distribution of the NOx catalyst 31.

  In S203, the degradation estimation unit 64 is caused to perform degradation estimation processing, as in S104 (see FIG. 4) of the first embodiment. Based on this S203, the deterioration estimation part 64 performs the process substantially the same as S142-S145 of 1st embodiment, and estimates the part which has deteriorated among the NOx catalysts 31. FIG. And the reduction | restoration control part 65 implements each process of S204-S209 based on the information of the degradation part estimated in the degradation estimation part 64. FIG. Each process of these S204-S209 is substantially the same as S105-S110 (refer FIG. 4) in 1st embodiment.

  When the correction of the reforming set in S207 and S209 is executed, the reduction control unit 65 performs fuel reforming by feedback control using the catalyst temperature detected by each of the catalyst temperature sensors 44a to 44c. The state can be adjusted to the target reforming state. In order to realize such control, the reduction control unit 65 estimates the distribution of heat generated by the reduction reaction in the NOx catalyst 31 (see the solid line in FIG. 10). The reduction control unit 65 can generate a distribution of generated heat in consideration of reaction heat of by-products (methane, ethylene, ethane, acetaldehyde, etc.) generated during fuel reforming. The details of the reforming adjustment process for adjusting the reformed state of the fuel with the estimated generated heat distribution as a target will be described below with reference to FIGS. 1 and 2 based on the flowchart of FIG.

  In S221, it is determined whether or not the warm-up operation of the internal combustion engine ICE has ended. If it is determined in S221 that the warm-up operation is being performed, the reforming adjustment process is terminated. On the other hand, if it is determined in S221 that the warm-up operation of the internal combustion engine ICE has ended, the process proceeds to S222.

  In S222, the steady state determination unit 63 determines whether or not the internal combustion engine ICE is in a predetermined operation state, that is, in a steady state. If it is determined in S222 that the internal combustion engine ICE is not in a steady state, the reforming adjustment process is terminated. On the other hand, if it is determined in S222 that the internal combustion engine ICE is in a steady state, the process proceeds to S223.

  In S223, the supply of the reducing agent is started under the control conditions after the reforming correction set in the reforming control process, and the process proceeds to S224. In S224, it is determined whether or not a predetermined time has elapsed since the supply of the reducing agent was started in S223. The specified time in S223 is a time for waiting for stabilization of the reduction reaction in the NOx purification device 30. In S224, it is determined that the specified time has elapsed, and when it is estimated that the reaction by the reducing agent added after the modification correction is stable, the process proceeds to S225.

  In S225, based on the temperature distribution of the NOx catalyst 31, a distribution of generated heat (refer to the solid line in FIG. 10) generated in response to the reaction of the reducing agent in each part of the NOx catalyst 31 is generated, and the process proceeds to S226. In S226, the generated heat distribution based on the actual measurement generated in S225 is compared with the estimated generated heat distribution (see the broken line in FIG. 10), and the process proceeds to S227.

  In S227, it is determined whether or not the two generated heat distributions compared in S226 are consistent. In S227, when the distribution of the generated heat based on the actual measurement matches the estimated distribution of the generated heat, the reforming adjustment process is terminated without performing the reforming adjustment. On the other hand, if it is determined in S227 that the generated heat distribution based on the actual measurement is deviated from the estimated generated heat distribution, the process proceeds to S228.

  In S228, the components related to the reforming, specifically, the fuel injection valve 21, the heater 22, the fuel pump 72, so that the distribution of the generated heat based on the actual measurement approaches the estimated generated heat distribution. Then, the control amount of the introduction control valve 83 is adjusted, and the process returns to S225. Then, S225 to S228 are repeated until the generated heat distribution based on the actual measurement matches the estimated generated heat distribution.

  In the second embodiment described so far, similarly to the first embodiment, since the catalyst portion with little deterioration can sufficiently exhibit the action of purifying NOx in the exhaust gas, the performance deterioration of the NOx catalyst 31 due to the deterioration is caused. It becomes possible to suppress.

  In addition, the deterioration estimating unit 64 of the second embodiment can estimate the degree of deterioration of the NOx catalyst 31 when the steady state determining unit 63 determines that the internal combustion engine ICE is in a steady state. According to the above, the fuel supply only for the diagnosis by the specific fuel injection pattern becomes unnecessary. In addition, the deterioration estimation unit 64 can complete the estimation of the degree of deterioration of the NOx catalyst 31 while the internal combustion engine ICE is operating normally.

  In addition, when the fuel reforming state is corrected, the reduction control unit 65 of the second embodiment performs the target reforming of the fuel reforming state by feedback control using the detection values of the catalyst temperature sensors 44a to 44c. It can be adjusted to the state. Therefore, the reducing agent whose reforming state is optimally adjusted to meet the current degree of deterioration reaches the NOx catalyst 31.

  In addition, in the second embodiment, the heat of reaction due to by-products is added to the distribution of generated heat that is a target in feedback control. If the reforming state of the fuel is adjusted so as to be consistent with the distribution of the generated heat, the catalyst portion with less deterioration can surely exhibit the NOx purification action.

(Other embodiments)
Although a plurality of embodiments have been described above, the present disclosure is not construed as being limited to the above-described embodiments, and can be applied to various embodiments and combinations without departing from the scope of the present disclosure. it can.

  In the above embodiment, the deteriorated portion is estimated by comparing the actually measured catalyst temperatures T01 to T03 and the reference temperatures T01B to T03B. However, a threshold value for determining deterioration, that is, the temperature between the catalyst temperature and the reference temperature. The difference ΔT can be changed as appropriate. This temperature difference ΔT may be zero, for example. Furthermore, the temperature difference ΔT may be set to be constant over the entire NOx catalyst, or may be set to gradually increase or decrease from the front toward the rear.

  In the above embodiment, a continuous linear temperature distribution is defined as the deterioration distribution based on the detection values of the catalyst temperature sensors 44a to 44c. However, the aspect of the deterioration distribution is not limited to the above aspect. For example, a deterioration distribution may be a data table in which the catalyst temperature measurement position and the actually measured catalyst temperature are simply linked.

  In the above embodiment, each of the catalyst temperature sensors 44 a to 44 c measures the catalyst temperature as a physical quantity related to the deterioration of the NOx catalyst 31. However, the physical quantity related to the deterioration of the NOx catalyst is not limited to the catalyst temperature. For example, information such as the oxygen concentration in the catalyst, the NOx concentration, and the hydrocarbon state may correspond to a physical quantity related to deterioration. As a configuration for detecting these physical quantities, a plurality of Ox sensors, NOx sensors, HC sensors, and the like can be provided in the NOx purification device as degradation detectors.

  Furthermore, the number and arrangement of deterioration detection units such as a catalyst temperature sensor may be changed as appropriate. For example, only two deterioration detection units may be provided in the NOx purification device, or four or more deterioration detection units may be provided. Further, the plurality of deterioration detection units may be arranged at equal intervals along the flow direction, or may be arranged at unequal intervals. Furthermore, the plurality of deterioration detection units may be arranged in a straight line along the flow direction, or some of the deterioration detection units may be offset with respect to other deterioration detection units.

  The steady state determination unit 63 of the above embodiment has acquired the transition of the gas flow rate of the exhaust gas and the fuel injection amount as operation information for determining the steady state of the internal combustion engine ICE. However, the operation information used when determining the steady state can be changed as appropriate. For example, the rotational speed of the output shaft of the internal combustion engine ICE, the intake air flow rate, and the like may be used for determination of the steady state. The steady state determination unit may determine the steady state when all the fluctuations of the plurality of operating information are within the threshold value, or may determine that the steady state is when the specific operating information is within the threshold value. May be.

  The reduction control unit 65 of the above embodiment adjusts the level of activity in the reformed fuel by complex control of the temperature and air-fuel ratio of the reformed fuel. However, the reduction control unit may be able to control only the temperature of the reformed fuel or only the air-fuel ratio, for example. Further, if the reformed state is feedback-controlled using the distribution of heat generated by the NOx catalyst as in the second embodiment, the configuration corresponding to the reducing agent sensor 45 (see FIG. 1) is omitted. Also good.

  In the above embodiment, the air that has been pressurized by the compressor section of the supercharger 11 is supplied to the reforming catalyst. However, the air pumped by the electric pump may be supplied to the reforming catalyst against the pressure in the exhaust pipe. With such a configuration, the ECU can increase or decrease the amount of air supplied to the reforming catalyst by controlling the discharge amount of the electric pump. Further, the configuration for introducing air into the reforming catalyst may be omitted.

  In the above embodiment, the functions provided by the processor 51 of the ECU 50 can be provided by hardware and software different from those described above, or a combination thereof. For example, a control circuit dedicated to post-processing provided separately from the ECU 50 that performs integrated control of the operation of the internal combustion engine ICE is a “purification control device” that includes one of reforming control processing, deterioration estimation processing, reforming adjustment processing, and the like. Some or all may be executed. Further, various non-transitional physical storage media such as a flash memory and a hard disk can be adopted as the storage medium 53 for storing the program executed by the processor 51 and each control map.

  In the above-described embodiment, the example in which the characteristic configuration of the present disclosure is applied to the exhaust gas purification system that purifies the exhaust gas discharged from the internal combustion engine mounted on the vehicle has been described. However, the characteristic configuration of the present disclosure can be applied not only to an internal combustion engine mounted on a vehicle but also to an exhaust gas purification system that purifies exhaust gas of an internal combustion engine or an external combustion engine mounted on a ship, a railway vehicle, an aircraft, or the like. is there. Furthermore, the characteristic configuration of the present disclosure can also be applied to an exhaust purification system that purifies exhaust gas of an internal combustion engine or an external combustion engine installed for power generation.

ICE Internal combustion engine (engine), 20 Fuel reformer (fuel reformer), 21 Fuel injection valve (fuel injection part), 22 Temperature riser (temperature rise part), 31 NOx catalyst (catalyst), 44a-44c Catalyst Temperature sensor (deterioration detection unit), 45 Reducing agent sensor (reducing agent detection unit), 50 ECU (purification control device), 62 Information acquisition unit, 63 Steady state determination unit, 64 Deterioration estimation unit, 65 Reduction control unit (reforming control) Part), 81 Fresh air introduction device (new air introduction part), 100 Exhaust gas purification system

Claims (14)

A fuel reformer (20) that generates a reducing agent that reduces nitrogen oxides contained in exhaust gas discharged from an engine (ICE) by reforming fuel used in the engine;
A catalyst (31) for purifying nitrogen oxides in exhaust gas using a reducing agent supplied by the fuel reformer;
A plurality of deterioration detectors (44a to 44c) that are arranged on the catalyst along the flow direction of the exhaust gas and detect a physical quantity related to deterioration of the catalyst;
A deterioration estimation unit (64) that generates a deterioration distribution of the catalyst in the flow direction based on detection values of the plurality of deterioration detection units, and estimates a portion of the catalyst with less deterioration from the deterioration distribution;
Exhaust gas provided with a reforming control unit (65) that controls reforming of the fuel by the fuel reformer so as to reach a portion with little degradation estimated by the degradation estimating unit in a state where the reducing agent is activated. Purification system.   The reforming control unit controls the activity of the reducing agent supplied from the fuel reformer to be low as a portion of the catalyst that has progressed deterioration expands downstream along the flow direction. The exhaust gas purification system according to 1. The fuel reformer has a fuel injection section (21) for injecting fuel,
The exhaust purification system according to claim 2, wherein the reforming control unit reduces the activity of the reducing agent by controlling to increase the amount of fuel injected from the fuel injection unit per unit time. The fuel reformer has a temperature raising part (22) for raising the temperature of the fuel,
The exhaust purification system according to claim 2 or 3, wherein the reforming control unit reduces the activity of the reducing agent by controlling the temperature of the temperature raising unit to be low.   The reforming control unit determines the activity of the reducing agent supplied from the fuel reformer when the deterioration estimating unit estimates that the downstream portion of the catalyst in the flow direction is deteriorated. The exhaust purification system according to claim 1, wherein the exhaust gas is controlled to be high. The fuel reformer has a fuel injection section (21) for injecting fuel,
The exhaust purification system according to claim 5, wherein the reforming control unit increases the activity of the reducing agent by controlling to reduce the amount of fuel injected from the fuel injection unit per unit time. The fuel reformer has a temperature raising part (22) for raising the temperature of the fuel,
The exhaust purification system according to claim 5 or 6, wherein the reforming control unit increases the activity of the reducing agent by controlling to raise the temperature of the temperature raising unit. The plurality of deterioration detectors detect temperatures at a plurality of locations of the catalyst,
The deterioration estimation unit compares the catalyst temperature (T01 to T03) detected by each of the deterioration detection units with a reference temperature (T01B to T03B) indicated by the catalyst before deterioration, and the detected catalyst temperature is low. The exhaust purification system according to any one of claims 1 to 7, wherein the portion is estimated as a portion where deterioration has progressed.   When the reforming control unit corrects the reforming state of the fuel according to the degree of deterioration of the catalyst estimated by the deterioration estimating unit, the reforming control unit uses the catalyst temperature detected by each of the deterioration detecting units, The exhaust purification system according to claim 8, wherein a reforming state of fuel supplied to the catalyst is adjusted.   10. The fuel reformer according to claim 1, wherein the reforming control unit causes the fuel reformer to start supplying a reducing agent for estimating deterioration of the catalyst when a preset diagnosis start condition is satisfied. The exhaust gas purification system according to one item. An information acquisition unit (62) for acquiring operation information indicating an operation state of the engine in time series;
A stationary determination unit (63) for determining whether or not the engine is in a steady state based on a transition of operation information acquired by the information acquisition unit;
The exhaust gas purification system according to any one of claims 1 to 10, wherein the deterioration estimation unit starts estimating the deterioration of the catalyst when the engine determination unit determines that the engine is in a steady state. . A reducing agent detector (45), which is located between the fuel reformer and the catalyst and detects the state of the reducing agent supplied from the fuel reformer;
The reforming control unit is supplied with the reducing agent from the fuel reformer based on the detection result of the reducing agent detection unit so that the reducing agent in an activated state reaches a part of the catalyst with less deterioration. The exhaust gas purification system according to any one of claims 1 to 11, wherein the degree of activity of the gas is corrected. A fresh air introduction part (81) for introducing air into the fuel reformer,
The said reforming control unit controls the introduction of air by the new air introducing unit so that the reducing agent in an activated state reaches a part of the catalyst that is less deteriorated. The exhaust gas purification system described in 1. A fuel reformer (20) that generates a reducing agent that reduces nitrogen oxides contained in exhaust gas discharged from an engine (ICE) by reforming fuel used in the engine;
A purification control device applied to an exhaust purification system (100) comprising a catalyst (31) for purifying nitrogen oxides in exhaust gas using a reducing agent supplied by the fuel reformer,
An information acquisition unit (62) that acquires a detection value obtained by detecting a physical quantity related to deterioration of the catalyst from each of a plurality of deterioration detection units (44a to 44c) arranged on the catalyst along the flow direction of the exhaust gas. When,
A deterioration estimation unit (64) that generates a deterioration distribution of the catalyst in the flow direction based on detection values of the plurality of deterioration detection units, and estimates a portion of the catalyst with less deterioration from the deterioration distribution;
And a reforming control unit (65) for controlling reforming of the fuel by the fuel reformer so as to reach a portion with little degradation estimated by the degradation estimating unit in a state where the reducing agent is activated. Control device.

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